A renowned clockmaker confesses to Dupin that he is being driven mad by the relentless ticking of a grandfather clock, a sound he believes is the amplified heartbeat of his deceased wife, whom he may have accidentally poisoned. Dupin investigates, discovering a complex series of intricate mechanisms and hidden chambers within the clock, revealing not guilt, but a desperate attempt by the clockmaker to preserve his wife's memory through a bizarre, almost alchemical, process that has inadvertently unleashed a spectral presence.